Did some checking. A popular charter to the Flower Gardens is the M/V Fling.
From their web site FAQ:
Also:
I know that 'follow the leader' guided group dives are common on some trips (particularly the Caribbean tourist-catering charter boat op.s). In that case, the scenario BuddaSummer lays out has been my experience with 2 tank cruise ship diving; you probably won't hit an NDL with 2 spaced out guided tourist dives, each with moderate-size groups all diving 80 cf tanks.
But if you dive an operation that lets you do your own thing, and stretch your bottom time if you can, it may be different.
Richard.